Bhudhiyamai said—“Forest is our ‘collective bank’—not yours or mine alone”. Are there other things which are our collective wealth? So if someone uses more, everyone would suffer?

Yes, there are some other things which are our collective wealth. Some examples are as follows:
(a) Groundwater (b) Fish in the rivers and sea
(c) Minerals (d) Fossil fuels such as coal and petroleum.